The present invention relates to a method and apparatus for wrapping paper and board rolls into a wrapper having a width smaller than the overall width of the roll.
In the paper industry, paper rolls are conventionally packaged into a wrapper wound about the roll and then headers are placed on the ends of the roll. The purpose of the wrapper is to protect the roll from moisture, mechanical blows and to facilitate automated handling without the risk of damaging the roll itself. Frequently, two or more narrow rolls are typically wrapped in the same package, whereby the wrapper must be made sufficiently strong to keep the package intact. The wrapper material is of a thick paper or board, which may be coated with a plastic or, alternatively, comprised of a multilayer structure of different materials. The rims of the wrapper are conventionally allowed to extend over the roll edges and they are then crimped over inner headers placed to the roll ends and glued in place with the help of outer headers. Typically, the wrapper width is selected to be sufficiently wide so as to extend over the entire width of the roll being wrapped and provide an overlap for crimping over the roll edges. Hence, a paper mill must keep a plurality of different wrapper widths available, because the widths of produced rolls are obviously dictated by the roll width orders placed by customer. Obviously, a wrapping machine designed to operate at different wrapper widths is very complicated and expensive, because it must have support means for wrapper rolls of different widths and equipment for dispensing each wrapper type of different width to the roll being wrapped.
The roll to be wrapped may alternatively be wrapped by winding a number of wrapper plies thereon. Glueing is used to assure a positive locking of the wrapper plies on the roll and sufficient strength of the wrapper. The glueing of the wrapper may be implemented by spraying on the wrapper surface a hot-melt glue, which may be applied as a stripe or dots. It is also possible to use a wrapper with a thermoplastic polymer coating that is hot-melted prior to winding the wrapper on the roll surface. Conventionally, the wrapping operation is carried out by first adhering the wrapper to the roll surface and then glueing the last plies of the wrapper to each other. U.S. Pat. No. 5,265,399 describes a method and apparatus for making a roll package by means of a wrapper having its surface coated with a layer of a thermoplastic binder. In this method, the binder coat on the wrapper surface is melted in order to adhere the leading end of the wrapper to the roll and the trailing end to the last plies when the wrapping operation is completed. Further, at least some of the wrapper plies are adhered by heat-melting to each other during the wrapping operation. The wrapper width is equal to the full width of the roll and the hot-melted area is controlled by zones in order to obtain desired glueing patterns and cope with different wrapper widths. Also in this method, a plurality of different wrapper widths are used, whereby the wrapper machine must contain several wrapper rolls. The number of wrapper rolls may be 10 and more, whereby at least a portion of the wrapper rolls will have a long dispensing distance from the wrapper roll to the roll being wrapped. This may cause problems in threading the leading end of the wrapper. A wrapper machine of the above-described type must have separate backstands for rolls of different widths or, alternatively, separate storage sites from which the rolls are fetched to the wrapping machine. As a result, such a wrapping machine requires a very large footprint.
Canadian Patent Application No. 2,184,857 describes a wrapping machine in which a wrapper narrower than the width of the rolls being wrapped is wound about the roll obliquely to the center axis of the roll. The wrapper is adhered by a flowable glue or binder to both the surface of the roll being wrapped and the overlapped portion of the wrapper plies. The wrapper is not wound up to the roll ends, but instead, they are left partially free and, after the obliquely wound portion of the wrapper is completed, the wrapper roll is rotated so that the roll ends can be wrapped with circumferential wrapper portions overlapping the roll ends. These wrapper portions that extend over the roll ends are crimped against the roll ends in a conventional manner. While this method manages using a single-width wrapper roll only, the width of the wrapper must be very narrow due to the oblique wrapping technique in order to achieve reliable wrapping and to avoid leaving an excessively large unwrapped area. at the roll ends. The method provides a two-ply wrap package, but as a consequence of the obliquely wound structure of the wrap, the strength of the package cannot be increased essentially by using a greater number of wrap plies. Due to the narrow width of the wrapper, the wrapper equipment has a limited capacity and operates at a slow pace, because the roll must be rotated over a great number of revolutions, during which the wrapper roll position must be altered and it must be moved between the ends of the roll being wrapped. Such roll rotating and transfer equipment makes the wrapper machine complicated with respect to its wrapping capacity and its complex construction increases the cost of the machine. Moreover, this technique is incapable of wrapping a number of rolls in a single package, because the narrow circumferential wrapper at least in a two-ply wrap fails to support the package reliably at the abutting inner ends of the adjacent rolls.
International patent application No. PCT/FI97/00322 discloses an apparatus for wrapping rolls wider than the wrapper width with a narrow wrapper using a plurality of overlapping wrapper plies wound over the entire length of the roll. In this apparatus, the rolls to be wrapped are brought to the wrapping station and first located therein by aligning their first ends with the edge of the wrapper. Next, a required amount of wrapper is wound about said first end of the roll and then the second end of the roll is aligned with the other edge of the wrapper, after which a second number of wrapper plies is wound about the roll. In this method, the wrapper width must be equal to the width of the narrowest roll to be wrapped, because the wrapper may not extend over the roll ends. This requirement results from the fact that the above-described wrapper apparatus is intended for such a wrapping technique in which no headers are placed to the roll ends, whereby the overlapping rims of the wrapper cannot be crimped against the roll ends. The wrapper is fixed in place by glueing in a conventional manner. While no detailed description is given for the applied glueing technique, conventionally roll packages are secured using, e.g., a hot-melt glue which is dosed in dots or stripes. Such a glueing method does not necessarily give a sufficiently strong and moisture-proof package when the wrap is made from a number of adjacent wrapper plies.
It is an object of the present invention to provide a method and apparatus suited for packaging paper and board rolls in a wrapper narrower than the roll width and simultaneously rendering a strong and highly durable package with a good moisture resistance.
The goal of the invention is achieved by wrapping the rolls to be packaged in a wrapping consisting of at least two plies of adjacent turns of a packaging wrapper having its surface coated with a hot-melting and cool-adhering binder material which is melted prior to the wrapping of the wrapper about the roll so that at least the first ply of the wrapper at the portion extending over the roll end is not heated and at least the superimposed portions of wrapper plies at the crimped wrapper edges and the overlapping portions of the adjacent wrapper plies are hot-melt bonded to each other.
Frequently, also the first ply of the wrapper facing the roll surface is hot-melt bonded to attach the wrapper to the roll and the last ply of the wrapper is entirely hot-melt bonded to achieve a tight and durable bond of the wrapper trailing end.
The invention offers significant benefits.
Today, packages of paper and board products are required to exhibit an extremely high performance. In addition to the need for protecting a roll efficiently during handling and transportation, the package must have a good appearance. In overlap wrapping, it is more difficult to attain a high quality as the wrapper wound about the roll comprises a plurality of adjacent plies. However, roll packages made by overlap wrapping are expected to be as good as those made from a full-width wrapper. The invention makes it possible to attain the same strength and moisture-proofness as those offered by a full-width wrapper, since now the wrapper plies can be hot-melt bonded to each other if so required. Prior-art techniques of attaching the wrapper have not been able to assure sufficient strength of the wrapper bond in the same fashion as the present invention. Through using a narrow wrapper web, also the width of the heating equipment can be made narrower, thus making the present wrapping system more cost-attractive than an apparatus based on wrapping with a wide wrapper. This is a significant benefit particularly in conjunction with the use of infrared heaters, because wide infrared heater systems are handicapped by a relatively high energy consumption. Furthermore, the wrapper need not necessarily contain a separate moisture-barrier layer, because the heat-sealable polymer coating can act as a sufficient moisture barrier if so required.
The width of the wrapper rolls can be selected optimally according to the packaging needs. Frequently, it is advantageous to have one wrapper width suited for the narrowest roll lo be wrapped and a second wrapper width for wrapping the most common widths of rolls inasmuch the proportion of rolls of a given width is very high in the overall production volume of a paper mill. By means of an optimal selection of wrapper widths, most of the rolls can be packaged with a single course of wrapper plies, whereby the capacity of the apparatus becomes high and no compromising in the flexibility of the packaging system is necessary. Moreover, the apparatus according to invention offers all the benefits attainable by virtue of overlap wrapping such as a smaller footprint of the apparatus and a reduced selection and inventory of wrapper materials. Owing to the ease of using a greater number of wrapper plies, wrappers of lower base weight can be used. Furthermore, the operating and investment costs of the apparatus are more profitable than those of conventional equipment. Significant savings can be attained in the use of the wrapper material as the top end of the roll can be wrapped with a wrapper of lower base weight than the bottom end of the roll which needs a wrapper of higher mechanical strength.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are intended solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.